- Unexpected Ice Tremors Disrupt Sea Level Rise Predictions
- A Surprising Discovery at the Heart of Glaciers
Researchers have uncovered numerous small ice tremors occurring deep within Greenland’s ice streams. Contrary to previous hypotheses that suggested these ice rivers flowed slowly like viscous honey, it appears they also exhibit a “stick-slip” movement.
To make this discovery, the research team used an optical fiber cable inserted into a 2,700-meter deep borehole, allowing for the first-time recording of seismic activity inside an ice stream.
- Glaciers Shake and Flow Simultaneously
A team led by Professor Andreas Fichtner from ETH Zurich made a major discovery: in the depths of ice currents, thousands of small earthquakes trigger each other and propagate over hundreds of meters.
This observation partially explains the discrepancies between current models of glacier dynamics and satellite measurements. It could also improve the simulations used to predict ice melt and sea level rise.
- Outdated Models and Uncertain Predictions
The ice currents of Antarctica and Greenland act like frozen rivers, transporting enormous quantities of ice to the ocean. Their speed and behavior directly influence future sea level rise, a crucial issue in climate change.
Until now, scientific models assumed that these currents flowed steadily and regularly. However, satellite observations show that these assumptions are incorrect: flow speeds vary significantly, rendering current estimates uncertain and potentially underestimated.
- Longstanding Ice Core Puzzles Finally Resolved
Ice tremors could also explain another long-observed anomaly: the presence of fault planes in deep ice cores. These fractures indicate internal tectonic movements within the ice, a known but previously unexplained phenomenon.
“This discovery is a key advancement in our understanding of small-scale deformations in ice currents.” — Olaf Eisen, Alfred Wegener Institute
The study was published in the prestigious journal Science and involved researchers from several institutions, including the Alfred Wegener Institute, the University of Strasbourg, the Niels Bohr Institute, and WSL (Swiss Federal Institute for Forest, Snow and Landscape Research).
- A Mysterious Connection Between Fire and Ice
Why had these ice tremors never been observed before? The answer lies 900 meters beneath the surface: a layer of volcanic particles prevents the propagation of seismic waves to the surface, masking the phenomenon.
These particles originate from a massive eruption of Mount Mazama (Oregon, USA) that occurred 7,700 years ago.
“We were stunned to discover this unprecedented connection between glacier dynamics and ancient volcanic eruptions.” — Andreas Fichtner
Researchers also found that impurities in the ice (notably traces of sulfates from volcanic eruptions) weaken its structure and promote the formation of microcracks, contributing to the ice tremors.
- A 2,700-Meter Borehole to Capture These Invisible Signals
The discovery was made possible through a fiber optic cable inserted into a 2,700-meter borehole, carried out as part of the East Greenland Ice-core Project (EastGRIP).
Once drilling was completed, scientists inserted a cable 1,500 meters deep and continuously recorded seismic activity for 14 hours.
This borehole is located in the northeastern Greenland ice stream (NEGIS), 400 km from the coast. It is the largest ice stream in Greenland, and its retreat is one of the main contributors to current sea level rise.
In this region, the ice moves toward the ocean at a speed of 50 meters per year.
- Towards a Revamp of Climate Models?
Researchers observed that these ice tremors are frequent and extend over a large area, suggesting that they could occur in all ice streams worldwide.
Source: Sain et Naturel
